[R] shrink a dataframe for plotting

[Thibaut Jombart]

Alexy Khrabrov wrote:

>I get tables with millions of rows.  For plotting to a screen-size  
>jpg, obviously just about 1000 points are enough.  Instead of feeding  
>plot() the original millions of rows, I'd rather shrink the original  
>dataframe, using some kind of the following interpolation:
>
>-- split dataframe into chunks of N rows each, e.g. 1000 rows each
>-- compute average for each column
>-- issue one new row of those averages into the shrunk result
>
>Is there any existing package to do that in R?  Otherwise, which R  
>idioms are most effective to achieve that?
>
>Cheers,
>Alexy
>
>
>  
>
Hi,

if you want to extract relevant information from such a table, splitting 
rows in arbitrary chuncks may not solve your problem. Ordinations in 
reduced space are designed for that kind of task, but hierachical 
clustering may also help. See Legendre & Legendre (1998, Numerical 
Ecology, Elsevier) for examples of such methods in Ecology, and the R 
packages ade4, vegan and hclust.

Regards,

Thibaut.

-- 
######################################
Thibaut JOMBART
CNRS UMR 5558 - Laboratoire de Biométrie et Biologie Evolutive
Universite Lyon 1
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Tél. : 04.72.43.29.35
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jombart at biomserv.univ-lyon1.fr
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